Synthesis and characterization of platinum(II) polymetallaynes functionalized with phenoxazine-based spacer. A comparison with the phenothiazine congener

Abstract

A new series of soluble, solution-processable metallopolyynes of platinum(II) functionalized with electron-rich phenoxazine–oligothiophene rings and their corresponding dinuclear model complexes were synthesized and characterized. The influence of the inclusion of thienyl rings along the polymer chain on the optical, electronic and photovoltaic properties of these metallopolymers was studied. The evolution of the singlet and triplet excited states in these metal-based materials was elucidated in detail. It is shown that addition of the thiophene rings can elevate the HOMO energy level of the polymers. The absorption edge of the oxygen analogue is more red-shifted than that of the sulfur congener, which is attributed to the stronger electron-donating ability of the phenoxazine unit than that of the phenothiazine group. The down-shifted HOMO level of the phenothiazine-based polymer is found to enhance the photovoltaic performance by increasing the open-circuit voltage of the polymer solar cell relative to the phenoxazine-based congener. At the same donor:acceptor blend ratio of 1:4, the light-harvesting capability and solar cell efficiency notably increase as the thienyl rings are added.